Low impact exercises to maintain a big butt?

So I injured my knee and I can't do anything that requires me to put pressure on it. (I can walk and stuff, but no squatting, lunging, etc. motions). I used to do a ton of squats, lunges, other butt exercises but I can't for a few weeks because of the injured knee. I like my big butt, I don't want it to get small. :( haha. So does anyone know any low impact exercises that will keep my butt big?
Low impact exercises to maintain a big butt?
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